server.js

const
	bitcore = require('bitcore-lib'),
	{PublicKey} = bitcore,
	{BufferWriter} = bitcore.encoding,
	{Signature, ECDSA, Hash} = bitcore.crypto,
	{sha256sha256, sha256} = Hash;

function verify(hiddenChallenge, visualChallenge, pubKey, signature, version) {
	hiddenChallenge = Buffer.from(hiddenChallenge, 'hex');
	visualChallenge = Buffer.from(visualChallenge);
	pubKey = new PublicKey(Buffer.from(pubKey, 'hex'));
	signature = Signature.fromCompact(Buffer.from(signature, 'hex'));

	let message;

	if (version === 1) {
		message = Buffer.concat([hiddenChallenge, visualChallenge]);
	} else if (version === 2) {
		message = Buffer.concat([sha256(hiddenChallenge), sha256(visualChallenge)]);
	} else {
		throw new Error('Unknown version');
	}

	const
		magicBytes = Buffer.from('Bitcoin Signed Message:\n'),
		prefix1 = BufferWriter.varintBufNum(magicBytes.length),
		prefix2 = BufferWriter.varintBufNum(message.length),
		buf = Buffer.concat([prefix1, magicBytes, prefix2, message]),
		hash = sha256sha256(buf);

	return ECDSA.verify(hash, signature, pubKey);
}

const
	hidden = "cd8552569d6e4509266ef137584d1e62c7579b5b8ed69bbafa4b864c6521e7c2", // Use random value
	visual = "2015-03-23 17:39:22",
	pubKey = "023a472219ad3327b07c18273717bb3a40b39b743756bf287fbd5fa9d263237f45",
	signature = "20f2d1a42d08c3a362be49275c3ffeeaa415fc040971985548b9f910812237bb41770bf2c8d488428799fbb7e52c11f1a3404011375e4080e077e0e42ab7a5ba02";

console.log(verify(hidden, visual, pubKey, signature, 2));